To troubleshoot foul odors lasagna garden beds produce, check two things first. You either have too much nitrogen in your layers or your bed is packed too tight for air to flow. Both problems cause the same bad smell and both have quick fixes.
When I first smelled a strong rotten egg odor from my newest lasagna bed, I knew something went wrong. The stink hit me from 10 feet away on a calm morning. I had piled on a thick layer of fresh grass clippings and topped them with only a thin layer of leaves. That was my mistake.
A friend of mine had the same issue after she added a big batch of kitchen scraps all at once. The sour smell hit within two days and her neighbors started to notice. She fixed it by piling 4 inches of dried leaves on top and poking holes along the edges with a garden fork.
Bad smells happen when your bed breaks down without enough air. This is called going anaerobic. When your nitrogen-rich green layers are too thick, they pack down and push out the oxygen. Microbes that work without air give off hydrogen sulfide and ammonia gas. That rotten egg or sharp chemical smell tells you your bed is rotting wrong.
Your healthy beds break down with plenty of air and give off carbon dioxide that you can't smell. The key is keeping your brown to green ratio right. MU Extension says you should use a 2:1 ratio of carbon to nitrogen by volume. Most smell problems come from having too little brown material in your stack.
The fastest lasagna garden bad smell fix takes about 15 minutes of work. First, spread a 4-inch (10 cm) thick layer of dry brown material on top. Dried leaves, straw, or torn cardboard all work great. This cap blocks the smell right away and gives microbes a carbon source to balance the excess nitrogen below.
Next, take a garden fork and push it into the bed along the edges every 6 inches. Wiggle it back and forth to open up small air channels. Don't flip or turn the layers. Just poke holes to let fresh air reach the packed spots. This smelly compost layers solution works within 24 to 48 hours in most cases.
Stop future smells before they start by capping every green layer with a brown layer at least twice as thick. If you add 2 inches of grass clippings, put 4 inches of leaves on top. Never leave green material exposed on the surface. This one habit stops almost every odor problem before it has a chance to start.
Read the full article: Lasagna Gardening Method in 10 Steps
